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IS 11244:1985 is the Indian Standard (BIS) for design and construction of elevated reinforced concrete water tanks. This Indian Standard outlines the code of practice for designing and constructing elevated reinforced concrete water tanks. It specifies the materials, loads (including hydrostatic, wind, and seismic), design principles based on the working stress method to ensure water tightness, and construction and testing procedures.
Covers recommendations for the design and construction of elevated reinforced concrete water tanks.
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Tanks, Silos and Storage Structures
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! This code is based on the Working Stress Method (WSM), not the modern Limit State Method (LSM). Permissible stresses are intentionally kept low to control cracking.
! While not officially superseded, current practice often involves using the more comprehensive IS 3370 (Parts 1-4) for general liquid retaining structures in conjunction with IS 1893 (Part 2) for seismic design of liquid retaining tanks.
! The primary design consideration for reinforcement is crack width control, not just yielding strength, hence the low allowable tensile stresses in steel.
Code Requirements for Environmental Engineering Concrete Structures and Commentary
Directly addresses the design of concrete tanks, reservoirs, and other environmental structures, including water tanks.
EN 1992-3:2006European Committee for Standardization (CEN), Europe
HighCurrent
Eurocode 2: Design of concrete structures - Part 3: Liquid retaining and containment structures
Provides specific rules for the design of structures intended for liquid containment or retaining liquids.
BS 8007:1987British Standards Institution (BSI), UK
MediumWithdrawn
Code of practice for design of concrete structures for retaining aqueous liquids
Historical equivalent that formed the basis for UK practice before the adoption of Eurocodes.
AS 3735-2001Standards Australia, Australia
HighCurrent
Concrete structures for retaining liquids
Specifies design and construction requirements for concrete structures intended to retain liquids.
Key Differences
≠IS 11244 is based on the working stress method for serviceability checks (e.g., limiting steel stress to control cracks) while primarily using the limit state method for strength. Modern codes like ACI 350 and Eurocode 2 are fully integrated into a Limit State Design (LSD) or Load and Resistance Factor Design (LRFD) philosophy for all checks, including serviceability.
≠Crack width control in IS 11244 is achieved by limiting steel stresses to fixed values (e.g., 150 N/mm² for HYSD bars in direct tension). ACI 350 and EN 1992-3 use more detailed calculations based on bar spacing, cover, and calculated steel stress under service loads to predict and limit crack widths to specific values (e.g., 0.1 mm or 0.2 mm).
≠Modern international standards have more stringent and detailed durability requirements based on exposure classes. For example, concrete cover in ACI 350 and EN 1992-3 is significantly higher for liquid-retaining faces (e.g., 40-50 mm) compared to the 25 mm specified in IS 11244.
≠Seismic design in IS 11244 refers to IS 1893. However, international standards like ACI 350 provide more detailed and integrated seismic provisions specific to liquid-retaining structures, including considerations for convective and impulsive hydrodynamic pressures using more refined models (e.g., two-mass model) and specific ductility requirements for the supporting structure.
Key Similarities
≈All standards prioritize watertightness as a key performance requirement, imposing stricter criteria for crack control and durability than for general building structures.
≈The fundamental principles of structural analysis, such as calculating hydrostatic pressure on walls and floors and considering loads like self-weight, water weight, wind, and seismic forces, are common across all codes.
≈All standards require a minimum amount of reinforcement for temperature and shrinkage control to mitigate cracking, even though the calculation methods and specified percentages may differ.
≈The use of a limit state design philosophy for the ultimate strength of the structure is a common thread, ensuring the structure can safely resist factored loads without collapse.
Parameter Comparison
Parameter
IS Value
International
Source
Minimum Grade of Concrete
M20 (20 N/mm²)
4,000 psi (approx. 28 N/mm² or M28)
ACI 350-20
Maximum Permissible Crack Width (Liquid Face)
0.2 mm
Typically 0.1 mm (0.004 in) for severe exposure, though 0.2 mm is a limit for less critical cases.
ACI 350-20 / EN 1992-3
Permissible Steel Stress in Direct Tension (Serviceability)
150 N/mm² (for Fe415/HYSD bars)
Not directly limited; crack width is calculated. Equivalent stress is often around 200 N/mm² but depends on bar size and spacing.
ACI 350-20
Minimum Concrete Cover (Water Face)
25 mm
50 mm (2 inches)
ACI 350-20
Minimum Wall Thickness
100 mm
Recommended minimum 200 mm (8 inches), 300 mm (12 inches) preferred.
ACI 350-20
Minimum Reinforcement for Walls (% of gross area)
0.3% reducing to 0.15% (for thickness 100mm to 450mm)
Typically 0.5% for temperature/shrinkage (Grade 60 rebar), reducible for thick sections. Varies by calculation.
ACI 350-20
Freeboard (minimum)
200 mm
300 mm (12 inches) or more depending on tank size and wind conditions.
AS 3735-2001
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Design methodWorking Stress Method (WSM)
Minimum grade of concreteM20
Maximum permissible direct tensile stress in steel (High Yield Strength Deformed bars)125 N/mm²
Maximum permissible direct tensile stress in steel (Mild Steel bars)115 N/mm²
Minimum reinforcement in walls (up to 100mm thick)0.3% of the gross cross-sectional area
Minimum freeboard150 mm
Key Formulas
Hoop Tension (T) = w * H * D / 2 — For circular tank walls, where w is density of liquid, H is depth, D is diameter
It uses the Working Stress Method (WSM), as detailed in Clause 5.
What is the minimum grade of concrete for the water tank portion?+
M20 is the minimum grade specified for parts in contact with water (Clause 6.1).
Does this code cover seismic design?+
Yes, it mandates that seismic forces shall be considered as per IS 1893 (Clause 4.3).
What is the procedure for testing the finished tank?+
The tank should be filled with water and inspected for leaks after 24 hours. The drop in water level over the next 7 days should not exceed a specified limit (Clause 13).